1. Field of the Invention
The present invention relates to a bus bar for connecting electrical components of a power electronics device for controlling an electric machine and an arrangement of the bus bar for measuring current and for connecting to the power electronics device for controlling an electric machine.
2. Description of the Related Art
Bus bars are used as a common connection point to connect electrical components to one another and to supply them with the necessary current. That is, a bus bar comprises a conductor or conductors for collecting electric currents and distributing them to electric components. For example, bus bars are used in particular in a power electronics device for controlling electric machines.
The electric machines controlled by the power electronics device having a bus bar may include synchronous machines for generating electrical power. The electrical power generated by the synchronous machine is then made available to an extremely wide range of loads. These loads are usually connected into electrical networks. An example of the electrical network includes an on-board networks for motor a vehicle. When the electric machine is used in a motor vehicle, limited installation space is available for the electric machine and for the components needed to control the electric machine, which also include the power electronics device. The individual components must therefore be configured to be as compact and space-saving as possible while simultaneously being sufficiently powerful. This is especially important in the motor vehicle industry, where new electrical components are constantly being introduced.
The power electronics device mentioned above is used to drive an electric machine. For this reason, high currents flow through the power electronics device during operation. Furthermore, to adequately regulate and monitor the electric machine, the currents flowing through the power electronics device must be measured.
In the prior art, separate current-measuring devices have been used for these current measurements. These current-measuring devices generally comprise a sensor and an evaluation device connected to said sensor. To carry out the current measurement, the sensor is connected to a conductor through which the current to be measured flows. In one known embodiment for measuring current, it is necessary for the conductor in which the current is measured to be present as an independent component. This conductor then has to be mounted on an appropriate base structure. The drawback with such an embodiment, however, is that a large number of components are needed, and contact has to be made between all of them one after another. Thus, the conductor used for the current measurement must be mounted on the base structure. The sensor must then be mounted and contact must be established with this current conductor. As a result, the production of such an arrangement for measuring current is complicated in constructional terms and therefore costly. Therefore, this arrangement has a particularly detrimental effect in the speed of mass production and in keeping down the cost of the automobile.
In a further known embodiment for measuring current, the current-carrying conductor used for current measurement is applied to a printed circuit board. Contact is then made between this current conductor and the sensor of the current-measuring device. However, the disadvantage here is that the ability of printed circuit boards to carry current is restricted. Current measurement using this technique is limited to a small current class and is therefore not suitable for the power electronics device described above in which high currents have to be measured.
The object of the present invention is to provide a bus bar with an arrangement for measuring current and power electronics in which even high currents can be measured in a cost-effective and simple device. The object of the present invention is also to avoid the problems of the prior art.
According to a first embodiment of the present invention, the object is achieved by a bus bar constructed in one or more layers for connecting electrical components for a power electronics device for controlling an electric machine. According to the present invention, the bus bar is defined in that it has at least one portion with a shaped section that is connected or connectable to a current-measuring device.
In this way, electrical currents may be measured in a manner which is simple to construct and inexpensive. The present invention is based on the basic idea that the separate current conductors which were previously required for the current measurement may be eliminated. Instead of a separate conductor, the current conductor is now formed by a portion of the bus bar. This portion is a shaped section which may be formed, for example, as a projection. In principle, the present invention is not restricted to a specific number or shape of the particularly formed portions of the bus bar. Instead, the configuration criteria are given by the requirements of the particular application.
Since the portion with a shaped section which is used for current measurement is a permanent constituent of the bus bar, the current-measuring methods used for measuring the current may be implemented cost-effectively even for high currents. To this end, the bus bar, and in particular the portion with a shaped section, must be designed appropriately. In addition, the previously required step of mounting the separate conductor used for the current measurement on a base structure is eliminated. As a result, the construction is simplified and the production costs are also reduced. The bus bar constructed in accordance with the present invention avoids the disadvantages described in the prior art.
The at least one portion of the bus bar having a shaped section provided according to the present invention is connected or connectable to a current-measuring device, via which the current flowing through the at least one portion is measured. More detailed explanations relating to the current-measuring device and to its connection with the portion of the bus bar follow in the further course of the description.
The bus bars according to the present invention may be constructed in one or more layers. If the bus bars are constructed in more than one layer, the individual layers may be connected to one another by a suitable process such as, for example, by a lamination process. In this case, individual layers may comprise conductive material and other layers may comprise an insulating material. The use of bus bars for providing a simple and safe option for supplying different loads with current is well known. However, the complicated cabling used in known bus bar arrangements is eliminated by the present invention such that the use of the inventive bus bar leads to space savings in relation to the installation space. This is particularly advantageous when the bus bar is used in a power electronics device for operating an electric machine in a motor vehicle.
In a preferred embodiment of the bus bar according to the present invention, the bus bar may advantageously be formed from one or more layers of copper or aluminum. Of course, other materials may also be used. However, an important characteristic is that the material used is a good conductor of an electric current. Therefore, the bus bar advantageously comprises one or more layers of solid copper.
The bus bar according to the present invention advantageously has a plate-like basic structure. Bus bars of this type are easily produced and may be connected up to a large number of electrical loads, while requiring only a small amount of installation space.
In a further embodiment, the at least one portion of the bus bar with a shaped section is constructed in the area of one of the ends of the bus bar. In a particular embodiment, the bus bar has a plate-like, rectangular basic structure and the portion with a shaped section is accordingly advantageously constructed in one or more corners of the bus bar. In this case, the portion may be constructed, for example, as a projection which is likewise rectangular, so that the portion via which the current measurement takes place projects beyond the side edges of the bus bar.
The bus bar may advantageously have an essentially T-shaped structure. In this case, the vertical leg of the xe2x80x9cTxe2x80x9d forms the basic structure of the bus bar and the at least one portion with a shaped section is preferably constructed in the transverse area, perpendicular to the leg, of the T-shaped bus bar. A bus bar constructed according to this embodiment may be produced simply and cost-effectively.
In a further refinement, at least one slot is provided in the portion with a shaped section to subdivide the current-carrying paths. The current-carrying conductor paths are normally machined into the bus bar during the production process. The slot or slots have the function of interrupting current-carrying paths within the bus bar and, as a result, of guiding the current in a different direction. The slot or slots in the at least one portion with a shaped section therefore have the function of routing the current to that point which is connected or connectable to a current-measuring device, described in more detail further below. The number and configuration of the slots may vary widely depending on the requirements of the particular application in which they are used.
The at least one portion with a shaped section may advantageously have an essentially U-shaped configuration. To this end, the portion is preferably constructed as a shaped section in the form of a rectangular projection. The interspace bounded by the two legs of the xe2x80x9cUxe2x80x9d is formed by the above-described slot.
According to a further aspect of the present invention, an arrangement for measuring current is provided, which firstly has a bus bar according to the invention and as described above, in which a current is to be measured. The arrangement further comprises a current-measuring device including a sensor and an evaluation device connected to the sensor.
The arrangement according to the present invention for measuring current allows the measurement of high currents using a simple construction and cost-effective method. In relation to the advantages, actions, effects and the functioning of the arrangement, reference is hereby made to all of the above explanations relating to the bus bar according to the invention.
In a preferred embodiment of the arrangement according to the present invention, the sensor for measuring the current is advantageously disposed physically close to the at least one portion with a shaped section of the bus bar. The sensor is not required to be connected directly to the at least one portion. Instead, the at least one portion of the bus bar and the sensor may be arranged physically separated and without any direct connection. The important factor is merely that the sensor for measuring the current in the bus bar is suitable, for example, in that it can detect a parameter which indicates the current flowing through the bus bar, such as, the electric and/or magnetic fields in the bus bar.
In another embodiment, the sensor is connected to the at least one portion of the bus bar with the shaped section such as, for example, by a suitable electrical connection.
The sensor is advantageously designed to measure an electric and/or magnetic field. Of course, other sensor elements which measure parameters indirectly or directly related to the electric current in the bus bar are also conceivable. In a further embodiment, the sensor may be designed as a sensor element based on magnetoresistance or on the Hall effect. Accordingly, the invention is not restricted to the two examples of the sensors described above. Any sensor that detects a parameter which indicates current in the at least one portion of the bus bar may be used.
According to a third aspect of the present invention, a power electronics device for controlling an electric machine is provided, which includes a power part having a plurality of capacitors and a plurality of power semiconductors. Furthermore, the power electronics device has a bus bar according to the invention and as described above, which is connected to the capacitors and the power semiconductors.
Electric machines are preferably driven via such power electronics devices. The currents flowing through the device may be measured in a simplexe2x80x94in particular a constructionally simplexe2x80x94and inexpensive way as a result of their configuration. In relation to the advantages, actions, effects and the functioning of the power electronics device, reference is again made to all of the above explanations relating to the bus bar according to the invention and to the arrangement for current measurement according to the invention.
The arrangement of the individual components according to the present invention provides a power electronics device of compact design, in which the individual components are disposed in an optimized way so that the arrangement of the individual components in the power electronics device allow the power electronics device to require only a small installation space. As a result, the power electronics device according to the present invention are particularly suitable for use in the motor vehicle sector. Furthermore, the special design of the bus bar allows the current to be measured directly on said bus bar via the current-measuring device. This considerably simplifies the production of the arrangement and therefore also leads to savings in costs.
The configuration of the power electronics depends to a great extent on the voltage level required. For this reason, the number of capacitors and power semiconductors may vary depending on the design of the power electronics device. Accordingly, the invention is not restricted to a specific number of capacitors and power semiconductors.
Suitable power semiconductors preferably comprise MOSFETs, IGBTs or other devices of similar characteristics and capacities. The choice of which of the suitable power semiconductors is to be used for a particular application is made on the basis of the power requirements on the particular application in which power electronics device is used. If the power electronics device is to be used, for example, within the framework of the 42 V on-board network planned by the automobile industry, via which in the future newly introduced electrical components such as, for example, windshield heating, electric valve operation and other components are to be operated, MOSFET devices are preferably used as the power semiconductors. IGBT devices are used, for example, at higher voltages.
The individual capacitors and power semiconductors are connected to the bus bar and wired and are therefore electrically interconnected via the bus bar.
The arrangement of power electronics device according to the present invention may advantageously be used for controlling a synchronous machine, more specifically, a permanently excited synchronous machine. In particular, the power electronics device according to the present invention may be used for controlling a starter generator such as, for example, a starter generator for motor vehicles. The starter generator may comprise an electric machine whose rotors are mounted over the crankshaft mounting of an internal combustion engine. This particular starter generator is used not only for starting and stopping the engine but may also perform various functions during engine operation, such as braking functions, booster functions, battery management, active vibration damping, and synchronization of the internal combustion engine.
An example of the type of power electronics device to be used in the arrangement according to the present invention are disclosed in German reference P 199 13 450, likewise filed by the applicant but not yet published, the content of which is incorporated herein by reference.
In a further preferred embodiment of the power electronics device according to the present invention, a number of terminals are advantageously provided, which are connected to the bus bar. The current to be collected and distributed by the bus bar is fed to the bus bar via these terminals.
In a further embodiment, at least one control printed circuit board is arranged with the bus bar and connected to the power semiconductors. The signal paths for the power semiconductors are also advantageously located on this control printed circuit board, in addition to other components.
In addition, a current-measuring device as provided in the arrangement for measuring current in the at least one portion of the bus bar according to the present invention described above, is advantageously arranged on the printed circuit board. This current-measuring device has a sensor and an evaluation device connected to said sensor, both of which are advantageously arranged on the control printed circuit board. The sensor and/or the evaluation device may be mounted on the printed circuit board using a conventional method such as, for example, surface mounted device techniques together with other components which are needed on the control printed circuit board. As a result, the intermediate step which was previously required in the prior art for mounting the current-measuring device or for making contact with the current-measuring device may be eliminated.
The joining of the bus bar and the control printed circuit board is effected normally during the mounting of the power electronics. The sensor for measuring current is brought into contact with the bus bar when the control printed circuit board is mounted on the bus bar.
In this case, the sensor is advantageously constructed underneath the at least one portion with a shaped section of the bus bar so that current measurement may be performed in the at least one portion. The sensor may be provided physically close to the at least one portion, but without contacting the at least one portion directlyxe2x80x94for example via a suitable electrical connection. If the sensor is located sufficiently close to the close to the at least one portion of the bus bar, the electric and/or magnetic fields generated by the current flowing through the bus bar may be detected by sensor to measure the current.
The particular advantage of the solution according to the invention as compared with the solutions disclosed by the prior art is that the components of the current-measuring device may be fitted to the control printed circuit board without additional effort during the production of the printed circuit board. After production of the control printed circuit board, the bus bar is subsequently connected to the control printed circuit board such that the at least one portion with the shaped section of the bus bar comes into operational contact with the sensor such thatxe2x80x94for example as described above a current measurement may be made. In the solutions disclosed by the prior art, on the other hand, it was necessary for the current conductor provided for current measurement to be fixed first onto a basic structure such as, for example, a printed circuit board by a separate operation. Furthermore, in a second intermediate step according to the prior art, the current-measuring device had to be fitted to the basic structure and contact had then to be made between the current-measuring device and the current conductor. These additional and complicated operation are now eliminated.
The control printed circuit board is preferably designed using Surface Mounted Device (SMD) techniques and performs all the control, monitoring and regulating functions of the power electronics, including the driving of the power semiconductors. For the control of the power electronics, a control device including a powerful microcontroller is preferably arranged on the control printed circuit board, all the functions advantageously being predefined via a Controller Area Network (CAN) bus. Depending on the requirement of the particular application, the control device may comprise further elements.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.